Thank you for your comments. Let me provide some more information.
Current Radio Installation
I currently drive a 2005 GMC Sierra extended cab pickup with 4 wheel steering and 4 wheel drive. (This truck turns on a dime and gives nine cents change.) I have installed a tri-band amateur radio that operates on the 440, 220, and 144 MHz bands. The radio is installed under to the dash over the transmission "hump" using simple "L" shape brackets. Power is supplied from an accessory 12V deep discharge AGM battery through a fused electrical distribution block, which are both in the engine compartment, then through the firewall (using a grommet to block environmental passage) to the radio. The one foot tall tri-band antenna is installed on the center of the cab roof, over the interior dome light, with the antenna cable routed down the left windshield post to the radio. The MNO antenna connector required creating a one inch hole in the roof. I like to think of my radio installation as a "professional" installation.
I would like to perform a similar radio installation on the Rivian.
Potential Issue: Radio Interference
Amateur radio installation may not be possible on the Rivian. The Rivian has a major computer driving the display screens and several safety related features such as the autonomous driving function. Since the Rivian is promoted as an outdoor adventure vehicle, I hope that the adventure includes using amateur radio. I expect that the safety related features will be protected from radio emissions from neighboring vehicles and fixed radio stations. However, a transmitter located inside the Rivian is another matter that will require testing for possible interference. Amateur radio operators can operate on up to 30 different bands ranging from 135 kHZ to over 250 GHz, using emission types CW, RTTY, SSB and data with maximum power of up to 200 watts on certain bands. As you can see my request for the ability to install amateur radio transmitters inside the Rivian requires a comprehensive test to ensure no interference to the Rivian computers and radios (AM broadcast, FM broadcast, cell phone, GPS, and other).
Please note that GM did not void the warranty due to the radio installation. The many computer chips located inside the GMC are not affected by the radiated energy from the antenna. The radio itself is totally surrounded by grounded metal to minimize spurious emissions. However the GMC does not have the computer or safety related functions as those of the Rivian.
What radio wiring I would like to be provided inside the Rivian
I am looking for a convenient way to provide power to the radio. A fused electrical distribution block that can service mobile radio transmitters, up to 20 Amps. A cigarette lighter plug is not recommended for amateur radio installations.
A 52Ω coaxial cable with a BNC, pl259, SMA, or N type connector on the inside of the cab. The antenna wire should be capable of being routed to the middle of the roof, the bed, or the frunk.

Most garage doors are too low to allow a roof antenna. So alternative antenna locations would be desirable.
Radio option
A hands free operated 2 meter 50 W radio would be a nice option to have in the Rivian.
An audio connection from the radio to the Rivian speakers would be a nice option to have in the Rivian.